The effect and nature of the radiation induced oxide-interface traps on the performance of the Yb2O3 MOS device

Abstract

Modifications in the crystal properties, chemical compositions and bond contents as a result of irradiation of Yb2O3/Si structures annealed at different temperatures in the dose range of 1-50 kGy were investigated. Beside, comprehensive results on the effect of the structural changes on radiation response of the MOS capacitors produced with these structures was presented in this study. 122 nm-thick Yb2O3 films were grown on p-type Si by RF magnetron sputtering, and the Yb2O3/Si structures were annealed at 200 degrees C, 400 degrees C, 600 degrees C, 800 degrees C under nitrogen ambient. The radiation exposure disrupts the crystalline properties of the film. Yb 4 d and O 1s spectra were taken from different depths in the Yb2O3/Si structures with X-ray photoelectron spectroscopy. Reasons of the right-side shift in the capacitance voltage (C-V) curves of the as-deposited and 200 degrees C-Yb2O3 MOS capacitors with radiation exposure were determined as increasing 2+ oxidation state occurring with the trapping of the electrons in the Yb3+ defect centers, decreasing Si-Si bond contents causing the positive charge trapping at Yb2O3/Si interface, existence of the hydrogen defect precursors. Events causing the left-side shift of the C-V with radiation exposure may be the silicate layer developing at the interface, increase in the trapping of the positive charges in the Si-Si defect centers, and decreasing Yb-Yb and 2+ contents. The radiation responses of the 400 degrees C, 600 degrees C, 800 degrees C-Yb2O3 MOS capacitors could not be measured at the frequencies lower than 2 MHz due to high charge trapping, high binding energies of the Yb-O and Yb3+ peaks, increasing 2+ oxidation content. The C-V curve shifted to the left-side at the relatively lower dose of 1 kGy for only device composed of 200 degrees C-Yb2O3 film. The sensitivities of the 200 degrees C-Yb2O3 MOS capacitor were found to be 16.3 mV/Gy for 70 Gy.